The Maximum Likelihood Detector which is also known as the Optimum Noncoherent Detector (or correlation detector) for detecting FSK signals in an additive white gaussian noise channel is well known. The performance of a correlation detector can also be achieved with other detector architectures such as a Matched Filter or a Fast Fourier Transform (FFT). However, the ability of these detectors to achieve a significant sensitivity improvement (i.e., 4 dB) over that of discriminators for 4-level orthogonal signalling (i.e. FLEX.TM.) and a significant sensitivity improvement (i.e., 3 dB) for 4-level quasi-orthogonal signalling (i.e. ReFLEX.TM.) depends greatly on the accuracy of the derived symbol synchronization. The output of the detector(s) is a discrete 4-level signal. Therefore standard edge detection or eye opening synchronization techniques can not be employed since they do not operate well at the lower sensitivity levels that are achievable by these optimum detectors. What is needed is a new synchronization technique that achieves performance greater than or equal to that of a hard wired clock and maintains the 4 dB and 3 dB improvements for FLEX.TM. and ReFLEX.TM. respectively. Furthermore, the new synchronization technique should provide for detectors for FLEX.TM. 4-level signalling in a static channel that have no phase performance imbalances.